A005441 Number of isonemal fabrics of period exactly n.

1, 1, 4, 4, 9, 8, 55, 21, 104, 62, 429, 196, 800, 698, 4674, 2070, 7721, 7154

Offset: 2

Author

Simon Plouffe

Keywords

• nonn
• more

References

• B. Grünbaum and G. C. Shephard, The geometry of fabrics, pp. 77-97 of F. C. Holroyd and R. J. Wilson, editors, Geometrical Combinatorics. Pitman, Boston, 1984. [gives different a(10) which is probably erroneous]
• N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

• Branko Grünbaum and G. C. Shephard, A catalogue of isonemal fabrics, Discrete Geometry and Convexity, 440 (1985), 279-298.
• B. Grünbaum and G. C. Shephard, An extension to the catalogue of isonemal fabrics, Discrete Mathematics, 60, (1986), 155-192.

Crossrefs

Cf. A000046, A193140, A262589.

Formula

a(n) = A000046(n) + A193140(n) + A262589(n).

Extensions

a(14)-a(19) from second Grünbaum and Shephard paper added by Sean A. Irvine, Jun 26 2016

a(10) corrected by Andrey Zabolotskiy, Apr 14 2023